The three fans are used in the same room. Can I use one remote for 3 fans?

You cannot, because every fan needs his own receiver otherwise he cannot receive the signal from the transmitter.

If you like to save money, because remotes are very expensive, you can use instead of a remote a wall speed regulator, only that it does not has different intensities for the light, only on/off, and you need a 5 wiring in the wall to controll fan and light separately.